The microarray

analyses showed significant changes of expression for SCO0934, with decreased levels of transcripts in both mutants (Figure  2 and Additional file 1: Table S1). The developmental INCB018424 chemical structure up-regulation in the wild-type strain and the lower transcript levels in the mutants were confirmed by qRT-PCR, although there was a limited up-regulation of this gene in the whi mutants. A low but significant signal was detected in spores from the SCO0934 promoter probe construct, but no phenotype was revealed in the SCO0934 deletion PD-332991 mutant (Figure  7 and Table  1). Thus, it remains unclear whether there is a sporulation-related role for this gene, which encodes a predicted membrane protein of unknown function. SCO1195 encodes a small predicted

membrane protein with similarity to the previously described SmeA protein that is produced during sporulation of S. coelicolor[41]. SmeA is required for the targeting of SffA, a protein with see more similarity to the SpoIIIE/FtsK family of DNA transporters, to sporulation septa, and several of the SmeA homologues in streptomycetes are encoded together with members of this protein family [41]. This is not the case for SCO1195, which instead may be co-transcribed with SCO1196, encoding a known substrate for secretion via the Tat pathway but of unknown function [42]. The results on SCO1195 expression were similar to those of SCO0934, with significant developmental up-regulation Fossariinae in the parent strain, lower expression in the whiA strain detected in the array experiments (Figure  2), and confirmation of this by real-time qRT-PCR (Figure  5). A SCO1195-1196 deletion mutant failed to reveal any obvious phenotype. Conclusions The aerial hyphal sporulation in S. coelicolor occurs only in a fraction of the colony biomass and is not highly synchronized. Thus, even if a gene is strongly induced

at a specific stage of sporulation, it is highly challenging to detect this change in global transcriptome investigations of total RNA extracted from the complex mixtures of cell-types that constitute a developing Streptomyces colony. We show here that by comparing a wild-type to mutants lacking key regulators that specifically act in processes linked to aerial hypha, it is possible to identify previously unknown genes that are up-regulated in sporulating aerial hyphae. These genes are not necessarily direct targets for transcriptional regulation by the WhiA or WhiH proteins. In fact, there is no clear ovelap between the set of genes identified here and the very recently described direct targets of WhiA in Streptomyces venezuelae[43]. Nevertheless, our approach allowed identification of several new genes that are important for sporulation in S. coelicolor.